x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: x86/hyperv: Fix NULL deref in set_hv_tscchange_cb() if Hyper-V setup fails Check for a valid hv_vp_index array prior to derefencing hv_vp_index when setting Hyper-V's TSC change callback. If Hyper-V setup failed in hyperv_init(), the kernel will still report that it's running under Hyper-V, but will have silently disabled nearly all functionality. BUG: kernel NULL pointer dereference, address: 0000000000000010 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP CPU: 4 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc2+ #75 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:set_hv_tscchange_cb+0x15/0xa0 Code: <8b> 04 82 8b 15 12 17 85 01 48 c1 e0 20 48 0d ee 00 01 00 f6 c6 08 ... Call Trace: kvm_arch_init+0x17c/0x280 kvm_init+0x31/0x330 vmx_init+0xba/0x13a do_one_initcall+0x41/0x1c0 kernel_init_freeable+0x1f2/0x23b kernel_init+0x16/0x120 ret_from_fork+0x22/0x30

References

• https://git.kernel.org/stable/c/b20ec58f8a6f4fef32cc71480ddf824584e24743
• https://git.kernel.org/stable/c/b0e44dfb4e4c699cca33ede431b8d127e6e8d661
• https://git.kernel.org/stable/c/9c177eee116cf888276d3748cb176e72562cfd5c
• https://git.kernel.org/stable/c/8823ea27fff6084bbb4bc71d15378fae0220b1d8
• https://git.kernel.org/stable/c/daf972118c517b91f74ff1731417feb4270625a4